# Comparing your costs between time periods Cost Comparison is a feature in Cost Explorer that helps you quickly identify and understand changes in your AWS spending. It automatically analyzes cost variations between two selected months, highlighting the largest cost drivers and explaining the reasons behind these changes. The feature provides both console and API access to help you analyze cost changes across your AWS spending. Key benefits: + Quickly identifies top cost changes across services, accounts, and Regions. + Provides detailed breakdowns of cost drivers, including usage and discount changes. + Reduces manual cost analysis time from hours to seconds. + Available in Cost Explorer at no additional cost. ## Permissions To access data in the Cost Comparison feature, you need the following IAM permissions: + `ce:GetCostAndUsageComparisons` + `ce:GetCostComparisonDrivers` These permissions enable you to retrieve cost and usage comparisons and cost drivers. ## Accessing the console To analyze your cost changes in the console, you can use either the **Top trends** widget or Cost Explorer. **To access the console** 1. Open the Billing and Cost Management console at [https://console.aws.amazon.com/costmanagement/](https://console.aws.amazon.com/costmanagement/). 1. Do either of the following: + On the console home page, view the **Top trends** widget, which shows the top 10 cost variations between the previous two months. + In the navigation pane, choose **Cost Explorer**, and then choose **Compare** in the **Report parameters** panel. Review the **Top Trends** widget regularly to identify significant cost changes early. For more information about this widget, see [Top trends](https://docs.aws.amazon.com/cost-management/latest/userguide/view-billing-dashboard.html#top-trends-widget). # Understanding how a cost comparison works You can use Cost Comparison to quickly understand your cloud spending by automatically identifying and unfolding the largest cost drivers driving the cost variations between two selected months. Cost Comparison provides a detailed breakdown for these cost variances, from usage shifts to changes in commitment-based discounts like Savings Plans coverage and applied credits, eliminating hours of manual investigation. The **Top trends** widget on the console home page automatically applies Cost Comparison to show the top cost changes across your services, accounts, and Regions. For more information about this widget, see [Top trends](https://docs.aws.amazon.com/cost-management/latest/userguide/view-billing-dashboard.html#top-trends-widget). You can use Cost Comparison in two main ways: + Query for any two months (referred to as baseline and comparison months) across any Cost Explorer dimension and cost metric. Cost Comparison analyzes your costs by: + Calculating the total cost for each selected dimension in the baseline month. + Comparing these with costs in the comparison month. + Ranking each resulting dimension value by the absolute cost difference. + Returning the top 10 increases or decreases for each dimension. **Example:** In the following example, Cost Comparison identified four services that demonstrated the largest change when comparing costs from March 2025 (comparison month) with April 2025 (baseline month): [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/cost-management/latest/userguide/ce-understand-cost-comparison.html) + Request detailed cost drivers for the cost change associated with a specific service, account, Region, or other dimension value. Cost Comparison: + Identifies the specific usage type driving the largest change. + Calculates the total cost for each charge type in the baseline and comparison months. + Ranks the results by absolute cost difference. + Provides a breakdown of cost changes for each charge type, allowing for targeted cost savings opportunities. **Example:** In the following example, Cost Comparison identified two RDS instances in Frankfurt, Germany (Europe Region) that accounted for a \$163,336.48 cost difference between the selected months. For each instance, Cost Comparison identified additional cost drivers and their impact. The first instance (EU-InstanceUsage:db.r6g.8xl) showed increased cost and usage alongside decreased reserved capacity coverage, suggesting an opportunity to purchase additional reservations if the higher usage is expected to continue. The second instance (EU-InstanceUsage:db.t4g.xl) showed increased cost and usage with a decrease in applied credits compared to the previous month. This instance requires investigation into both the usage increase to evaluate potential reserved capacity purchases and the unexpected reduction in credits. [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/cost-management/latest/userguide/ce-understand-cost-comparison.html) If you need to analyze cost changes for specific areas of your business, choose filters to focus on other dimensions like tags or cost categories. Cost Comparison supports all of the available cost metrics (unblended, net unblended, net amortized, etc.) options in Cost Explorer, giving you flexibility to view the data in the way that is most meaningful for your needs. Cost Comparison dynamically updates the drivers based on the specific cost metrics or dimensions you select. # Performing a cost comparison You can compare costs between any two months within the last 13 months to identify and understand changes in your AWS spending. If you have enabled multi-year data at monthly granularity, you can go back up to 38 months. For more information, see [Configuring multi-year and granular data](https://docs.aws.amazon.com/cost-management/latest/userguide/ce-configuring-data.html). **Note** To access data in the Cost Comparison feature, you need IAM permissions. For more information, see [Permissions](https://docs.aws.amazon.com/cost-management/latest/userguide/ce-cost-comparison.html#ce-cost-comparison-permissions). **To perform a detailed cost comparison** 1. Open the Billing and Cost Management console at [https://console.aws.amazon.com/costmanagement/](https://console.aws.amazon.com/costmanagement/). 1. In the navigation pane, choose **Cost Explorer**. 1. In the **Report parameters** panel, choose **Compare**. 1. For **Date range**, choose between: + **Relative (Month over month)**: Compare current month to previous month. + **Absolute (Custom)**: Compare any two months within the last 13 months (or up to 38 months if you have enabled multi-year data at monthly granularity). 1. Under **Group by**, choose a **Dimension** (for example, Service, Linked account, Region, Tag). **Note** Group by resource is not available for cost comparisons. 1. Apply additional filters to narrow your analysis to specific services, accounts, or other cost dimensions. **Note** Filter by resource is not available for cost comparisons. 1. View the detailed breakdown of cost changes: + Examine the graph and table displaying the cost comparison between the two selected periods. + Review the top 3 cost comparison drivers automatically highlighted by Cost Explorer. These show the most significant factors contributing to cost changes, whether increases or decreases. + Choose **View all** to see a comprehensive list of all cost comparison drivers. + For each cost comparison driver, Cost Explorer provides specific reasons for the change in costs, including usage changes, discount changes, and other charge types (for example, fees, credits). + Use the available Cost Explorer filters in **Report parameters** to analyze different aspects of your business. The graph and table are updated in real time, allowing you to analyze specific services, accounts, tags, or other dimensions to gain deeper insights into your cost changes.